Field
Embodiments of the invention relate to designs of, and methods of using, an RF ablation catheter together with optical tissue inspection.
Background
Radiofrequency (RF) ablation is a medical technique to produce tissue necrosis. It is used to help treat different pathologies including cancer, Barret's esophagus, or cardiac arrhythmias, among others. The application of alternating current with an oscillating frequency above several hundreds of kHz avoids the stimulation of excitable tissue while delivering heat by means of the Joule's effect. The increase in tissue temperature produces denaturation of the biological molecules, including proteins such as collagen. Traditionally, RF ablation is done by placing an external electrode on the patient's body, and applying an alternating potential to the tip of a catheter that is placed in contact with the tissue to be treated within the patient's body. The ablation effect depends on a number of factors, including applied electrical power, quality of the electrical contact, local tissue properties, presence of blood flow close to the tissue surface, and the effect of irrigation. Because of the variability of these parameters, it is difficult to obtain consistent results.
Indeed, this procedure has shown only limited effectiveness when used in atrial fibrillation, with individual success rates strongly dependent on the expertise and ability of the clinician performing it. Even in qualified centers, in the acute phase after ablation, successful treatment rates only go up to 80%, while recurrences in a year follow-up period may reach 20%. Some factors associated to recurrent cases are discontinuous ablation lines and incomplete wall ablation. Incomplete ablation resulting in edema rather than complete necrosis cannot be properly identified with current tools.
One further problem with catheter ablation is the long intervention times that are required in point-to-point procedures in the atrium. In these cases, continuous lines are created in a pre-defined pattern around anatomical structures to obtain the desired electrical isolation effect. Since ablation is done locally, a large number of individual lesions are commonly concatenated. Ensuring the continuity of such a pattern in a beating heart requires painstaking work and attention. Since the procedure is often performed with the support of fluoroscopy, it can pose a significant radiation dose to the clinician and the patient.